Capacitor mismatch auto-compensation for MEMS gyroscope differential capacitive sensing circuit

Abstract

A capacitor mismatch auto-compensation circuit has been designed and implemented for MEMS gyroscope differential capacitive sensing circuit. An in-chip capacitor array that controlled by the 7-bit SAR is selected to be connected in parallel with one of the gyroscope capacitor, making the two differential capacitors of the gyroscope equal. The compensation progress only takes eight periods of the clock at the start and will be turned off afterward automatically. The chip is fabricated in a 0.35um CMOS process. The test of the chip is performed with a vibratory gyroscope on the condition of a closed-loop control in the drive mode, and the measurement shows that the minimum capacitive compensation is 3.5fF.